A call setup phase must precede any data transfer over a connection-oriented network. A communication phase follows during which data is sent through the established connection. When communication is no longer required, the connection must be disconnected to "free" resources in the intermediate nodes so that other connections may later be made. Circuit switching is an example of a connection-oriented system.
The term connection-oriented refers to the fact that all communication is conducted using a connection through the intervening nodes (often called switches or routers). The connection must be established prior to being used, by first issuing connection service request. This sets appropriate information in each node through which the connection passes. This information remains in place until the end of the communication, at which point the connection is said to be "Cleared" and the capacity is released.
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